1. Field of the Invention
The present invention generally relates to a sensor for sensing the direction or the azimuth of a physical quantity such as a magnetic filed or gravity, a lead frame to be included in the sensor, and a method of manufacturing the sensor.
Priority is claimed on Japanese Patent Application No. 2005-42133, filed Feb. 18, 2005, and Japanese Patent Application No. 2005-88180, filed Mar. 25, 2005, the contents of which are incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
In recent years, terminal devices have been developed such as mobile phones with a GPS (Global Positioning System) function, which indicates information about a user's position. The terminal device may have an additional function of sensing or measuring geomagnetic field or acceleration, thereby sensing or measuring the azimuth or direction in a three-dimensional space of a user's terminal device or a motion of the terminal device.
In order to provide the terminal device with the above-described additional function, it is necessary to integrate the terminal device with one or more sensors such as magnetic sensors or acceleration sensors. In order to allow the sensor to detect the azimuth or acceleration in the three-dimensional space, it is necessary for the sensors to be sloped so that a first one of the sensors tilts from a second one. The sensors are mounted on stages that are included in a lead frame. Thus, the stages are also sloped so that a first one of the stages tilts from a second one.
A wide variety of sensors that sense physical quantities have been developed. A typical example of the sensor may include, but is not limited to, a magnetic sensor that senses a magnetic field. This magnetic sensor is different from the above-described sensor. This magnetic sensor has a substrate and magnetic sensor chips that are disposed on a surface of the substrate. The magnetic sensor includes first and second magnetic sensor chips that are mounted on the substrate. The first magnetic sensor chip extends parallel to the surface of the substrate. The second magnetic sensor chip extends vertically to the surface of the substrate. The first magnetic sensor chip senses first and second magnetic components of an external magnetic field. The first magnetic component is a component in a first direction that is parallel to the surface of the substrate. The second magnetic component is another component in a second direction that is parallel to the surface of the substrate and is perpendicular to the first direction. The second magnetic sensor chip senses a third magnetic component of the external magnetic field. The third magnetic component is still another component in a third direction that is vertical to the surface of the substrate and also vertical to the first and second directions. The magnetic sensor utilizes a pair of the first and second magnetic sensor chips to detect a three-dimensional vector that represents the geomagnetic field. As described above, the second magnetic sensor chip extends vertically to the surface of the substrate. This increases a thickness of the magnetic sensor that includes the first and second magnetic sensors. The thickness is defined as a dimension or a size of the magnetic sensor in a direction vertical to the surface of the substrate.
In order to reduce the thickness of the magnetic sensor, it is effective and advantageous to dispose magnetic sensor chips on sloped stages that are sloped or tilted from the frame body. Japanese Unexamined Patent Application, First Publication, Nos. 9-292408, 2002-15204, and 2004-128473 disclose examples of the conventional sensor which includes a frame body, sloped stages, and sensor chips that are mounted on the sloped stages. Japanese Unexamined Patent Application, First Publication, No. 9-292408discloses an acceleration sensor that includes a substrate and acceleration sensor chips that are sloped or tilted from a surface of the substrate, and a packaging that is placed on the substrate. The sloped sensor is highly sensitive to an acceleration in a direction that tilts from the surface of the substrate. The sloped sensor is poorly sensitive to another acceleration in another direction that is parallel to the surface of the substrate.
FIG. 17 is a plan view illustrating a conventional example of a lead frame to be used for forming a sensor that senses a physical quantity. FIG. 18 is a fragmentary cross sectional elevation view illustrating a sensor including the lead frame of FIG. 17. A lead frame 50 includes stages 55 and 57 that respectively support sensor chips 51 and 53, a frame body 59 that surrounds the stages 55 and 57, and connection portions 61 that connect the stages 55 and 57 to the frame body 59. This lead frame 50 is used to form a sensor. The stages 55 and 57 that respectively mount the sensor chips 51 and 53 are sloped from a plane that includes the frame body 59 and the connection portions 61. The lead frame 50 is placed in a cavity of dies “P” and “Q”. A molten resin is injected into the cavity to form a resin mold that encapsulates the magnetic sensor chips 51 and 53 and the stages 55 and 57. In the injection molding process, the sloped stages 55 and 57 are pushed by flow of the molten resin when injected in the cavity, thereby making it possible to change slope angles of the stages 55 and 57. Substantive change of the slope angles of the stages makes it difficult for the sensor to perform a desired function of accurately sensing a physical quantity.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved apparatus and/or method. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.